Edge trimming tape and method of manufacture

ABSTRACT

The present invention provides an adhesive filament-bearing adhesive tape comprising an adhesive substrate adapted to be releasably adhered to a surface to be coated, and a filament releasably adhered to an edge of that substrate, that is useful in trimming a coating applied to a surface.  
     The invention further provides a method of trimming a coating applied to a surface comprising applying to the surface to be coated a masking material to define the area to be coated and a filament of material of sufficient tensile strength to cut the coating material; applying coating material to the surface; allowing the coating material to cry or cure until it obtains sufficient strength to hold a cut edge; and drawing the filament through the coating to cut the coating.  
     Finally, the present invention provides an apparatus for making a filament-bearing adhesive tape comprising means for folding an adhesive substrate along a predefined line; means for applying a filament to the interior of the fold so formed; and means for closing said fold to retain said filament at the edge of the filament bearing tape.

TECHNICAL FIELD

[0001] The present invention relates to a method of trimming or cuttinga coating material that may be applied to a relatively smooth surface,and is particularly useful for trimming or cutting a curable materialsuch as polyurethane or paint without damaging the surface to which itis applied.

BACKGROUND ART

[0002] It has become increasingly common to apply a curable coating,such as a polyurethane, to an exposed surface such as a wall, floor orautomobile body to offer protection against, for example, corrosion,moisture or abrasion. These coatings are often applied by spraying,rolling or painting the coating material on to the surface to beprotected, and allowing the coating material to dry or cure in place.

[0003] Some polyurethane coatings as well as other high strengthcoatings are available for application in the form of a single componentformulation.

[0004] Many commercially useful coating materials, such as paints,epoxies, varnishes, polyurethanes and other coating materials areavailable in the form of, and are formed from, two or more componentswhich may be blended together immediately before application and appliedto the surface to be coated by a dynamic mix spray gun. The componentsmay be separately fed to the spray gun and mixed in the gun just beforethe coating material is sprayed on the surface to be coated. Thisprocedure, described in more detail in, for example, the applicant'sU.S. Pat. No. 5,388,761, provides a composition which will react onmixing to form a generally stable, substantially solid material soonafter application to the surface to be coated, thus minimizing dryingand curing time, and permitting the application of the coating materialto vertical and other non-horizontal surfaces. A properly trainedoperator can apply a coating of relatively uniform thickness to almostany appropriate surface.

[0005] In the case of some of these materials, such as polyurethane, theliquid components may be selected to react with one another almostimmediately to create an essentially solid, form-retaining product soonafter contact with the surface to be coated. Therefore, the componentsare most commonly kept separated from one another and mixed together inthe spray gun immediately before a coating of the material is to beapplied to the surface.

[0006] The ratio of various components can be varied to provide thedesired curing time and rate. For example, in the case of polyurethane,the two relevant components—isocyanate and polyol—may be prepared in avariety of formulations depending upon the application. Suchformulations are often intended to be combined in the 1:1 ratio byvolume. However, other mixing ratios, such as 5:1 and 1:5, are notuncommon. The appropriate mixing ratio for any particular applicationmay also vary with environmental conditions, such as temperature, whichaffects the reactivity of the materials, viscosity or other physical orchemical properties of the components of the mixture.

[0007] Applying such a rapidly drying or curing mixture to a surface tobe protected permits a quick and relatively uniform application of thecoating material to the entire surface and shortens the time requiredbefore the coated surface may be put to its normal or intended use.However, the coating must be applied relatively quickly, and applyingthe mixture by spraying, rolling or painting often requires maskingthose areas of the surface that are not intended to be coated beforeapplication of the coating, to protect those areas from unwanted coatingmaterial. Subsequent trimming of the coating material is common toremove unwanted coating material after the coating is applied, either toprovide access to the areas that ought not to be coated, such as drainsor electrical outlets, or to provide a neat appearance.

[0008] One particularly useful application is the increasingly commonuse of spray-on coatings for liners of boxes of pick-up trucks, andinteriors of vans and trucks. This application is one in which theappearance of both the coated and uncoated surfaces is particularlyimportant, and one in which a significant amount of masking may berequired. Such a spray-on liner provides protection against thecorrosive elements in the atmosphere and also against the abrasioncaused by various materials that may be carried in the truck, van orbox.

[0009] These spray on linings have several advantages over the moreconventional protection afforded by premoulded plastic liners that areinserted into the box of a pickup truck. Premoulded plastic liners donot form a water-tight seal with the body of the truck, and permit theentry of water and dirt between the liner and the truck body. This mayresult in substantial abrasion and corrosion to the body of the truckwhich is, however, not visible through the opaque liner. The loose fitof the liner results in movement of the liner against the body of thetruck, increasing the abrasion damage to the truck body.

[0010] Spray-on linings, however, provide a coating, typically ofpolyurethane, that is tightly bonded to the truck body, and which doesnot permit the entry of dirt or moisture between the lining and thetruck body. Also, the flexible properties of the polyurethane coatingoffer a slip resistant as well as protective surface for the cargo toride on. In the case of a lining for a pick up truck box, the lining isgenerally applied to the floor and side walls of the box and to someportion of the top rails and side body. It is important to provide aneat edge along the perimeter of the box. The rear of the box isgenerally masked to avoid applying any coating to the hinges andlatching mechanism, and the tail gate is generally removed and thesurface facing into the box of the pickup truck is coated separately.Both this surface, and the ends of the side and bottom surfaces of thebox must be trimmed to permit proper opening and closing of the door aswell as providing a neat appearance.

[0011] As in the case of painting or other surface applications, thesurface area that is actually covered by the sprayed on material may bedetermined by masking the surface that is not intended to be coveredwith masking tape and other commonly used masking material. The materialto be sprayed on the surface is intended to adhere firmly to thesurface. The use of masking materials prevents contact between thoseportions of the surface that are not intended to be covered, and allowsthe rapid application of the material only to the surface which isintended to be covered. In these operations, masking tape or othermasking material is used, which has an adhesive coating that issufficiently strong to hold the masking material in place while it isintended to be there, and yet permits the easy removal of the maskingmaterial when it is no longer required, while leaving no significantamount of adhesive material on the surface to be protected. The use ofthe term adhesive throughout this application generally refers to aremovable adhesive having these general properties.

[0012] After the application of the coating material, however, sometrimming is required to remove the coating material. This is commonlydone by cutting the coating material along the boundary of the maskedarea, to separate the coating that is to remain in place, and which willbe firmly bonded to the truck body, from the coating material that is tobe removed, which should not have contacted the truck body and whichshould be separated from the truck body by the masking material. Oncethis separation is made, it is possible to remove the masking tape orother masking material, and the unwanted surface coating. It is thusimportant in such a trimming application to cut precisely along the edgeof the masking material so that no masking material is left on thesurface beneath the coating. This would result in a portion or area ofcoating material that is not adhered to the surface to be protected,which could subsequently result in the peeling of the protective coatingfrom the surface. Conversely, if the cut is away from the masked edgeand into the area which is intended to be coated, removal of the coatingfrom the masked area will be more difficult and may result in theremoval of paint from the truck body.

[0013] One difficulty posed by the use of the relatively thick,abrasion-resistant coatings, such as polyurethane coatings, is thedifficulty in locating the edges to be trimmed. Furthermore, while theremoval of masking material used in painting effectively acts as an edgetrimming method, tearing or cutting the paint layer as the maskingmaterial is removed, conventional masking materials will not tearthrough the polyurethane coating, and often cannot be located under therelatively thicker coatings of poyurethane such as those used to line atruck box.

[0014] Various methods have been developed to overcome this difficulty.For example, several layers of masking tape may be used and layersremoved sequentially so that each layer of masking tape removesindividual thin layers of the coating material before the coating beginsto cure. This procedure generally requires extra personnel, is atime-consuming method that leaves a relatively rough edge to the coatingmaterial as well as an inferior bond at the extreme edge of the coating.

[0015] The most common way of trimming such coatings is simply bycutting the coating along the edge of the masking material with a knifeor other sharp instrument. This requires, first of all, locating theedge of the masking material, and then cutting the protective coatingwith a sharp instrument such as a knife. This almost invariably has theresult of cutting or scoring the underlying surface, which is aparticular problem with painted surfaces such pick-up truck beds andrequires that the line cut or scored into the truck bed to be repaintedbefore the vehicle can be delivered to the consumer.

DISCLOSURE OF THE INVENTION

[0016] The present invention provides a simple and cost-effective methodfor cutting the protective layer without in any way damaging theunderlying area or underlying surface which is intended to be protected.

[0017] According to the present invention, there is provided a means forcutting a protective layer which comprises applying a layer of maskingmaterial to delineate the surface to which the protective coating is tobe applied, and adhesively securing a thin, strong filament of wire orother suitable material to the surface of the masking material along theline of the edge to be trimmed. The ends of the wire are bent away fromthe surface so that they may be located after the spraying operation iscompleted.

[0018] The coating material may then be applied to the surface to beprotected and allowed to cure until the material has enough greenstrength or in other words is sufficiently cured to be form-retainingand to have developed adequate adhesion strength to the surface to whichit has been applied. Adhesion strength is important in that the edge ofthe coating that remains on the surface must not in any way releaseduring the trimming operation. The exposed end of the wire is locatedand used to pull the wire away from the surface and up through theprotective coating, thereby cutting the protective coating along themasking line, and subsequently removing the masking material, leavingthe unmarked surface of the vehicle with the desired coating in place.

[0019] The filament used to cut through the coating may vary dependingon the force required to cut through the coating. A common music wirewith a diameter as small as seven thousandths of an inch (0.007″) isadequate for cutting many polyurethane coatings up to a certainthickness and cure time. The masking materials commonly used in thepainting and coating of motor vehicle bodies and other surfaces arecapable of being applied to both curved and straight lines, to definethe surface to be painted or coated. Similarly, the thin filament may beapplied along the edge of a curved line to cut the coating materialalong a curve. A small steel wire size also makes it easy to form andadhere the filament to the surface as it is positioned around tightbends and curvatures. However, a disadvantage of the smaller wire isthat it may break while pulling the wire through a thick coating or aharder coating with a high tear strength factor. In this case thefilament could be a larger diameter wire size with a higher breakingstrength while still maintaining as high a degree of flexibility aspossible.

[0020] A metal wire with a rectangular or triangular profile could beused. The filament could also be a glass or synthetic fiber, or astrand, consisting of multiple twisted or braided filaments of variousmaterials, profiles and sizes.

[0021] The present invention further provides a self-adhesive,filament-bearing tape which is particularly suited to carrying out themethod of the present invention, and an apparatus which is adapted toeasily and quickly manufacture the said self-adhesive tape.

[0022] The present invention also provides an adhesive filament carryingtape which may be applied to the surface to be coated to position boththe masking material and the filament at the desired position. In itssimplest form, the tape comprises a substrate having at least oneadhesive surface which may be removably adhered to the surface to becoated, and a filament releasably adhered to an edge of the substrate.The tape may have a second adhesive surface to which additional maskingmaterial may be secured, or may itself be wide enough to act aseffective masking material. As with other single or double sided tapes,a non-adhesive release liner may be applied to any adhesive surface tofacilitate storage and handling of the masking tape, and removed whenrequired.

[0023] The invention also provides a machine adapted to manufactureadhesive tape according to one embodiment of the invention. The machinecomprises means for folding an adhesive tape to form a V-shape, meansfor applying a filament to the bottom of the V, and means for closingthe V to secure the filament at the folded edge of the tape. The machinealso provides optional means for applying or removing a release layer tothe folded tape and for rolling the tape onto a spool for storage anduse.

[0024] Although the present invention is described with particularreference to the coating of truck bodies, it will be understood that thepresent invention may be used in many other situations in which acoating must be cut or trimmed after application.

[0025] For example, a tub or tank may be manufactured of wood or othersuitable materials and made waterproof by spraying on the interiorsurface a coating of polyurethane or other appropriate material. Themethod and materials of the present invention may be used not only totrim the edges as required but also to cut any required apertures in thecoating for plumbing or other connections.

[0026] Another application contemplated for the cutting and trimmingmethod and tape of the present invention is in the trimming ofautomotive paint, or other paint coatings, when that paint is appliedautomobile body components or other surfaces on which it is intended toproduce a “two-tone” finish, that is, two paint colours meeting at asharply defined line. The use of the methods and articles of the presentinventions results in a superior edge finish when desired over a typicaledge finish using the usual methods of the prior art, such as usingmasking tape. In the methods of the prior art one of the paint coats maybe applied and after it is dry masking tape or a similar material isused to define the edge. Paint is applied up to and over the edgedefined by the masking tape, and the masking tape is pulled away to cutthe coating. The cutting of the coating by the filament of the presentinvention produces a more precise definition of the edge to the finishcoating material. The difference in appearance of the finished edge isthe result of cutting through the coating using the wire filament ratherthan tearing or breaking the coating material by pulling the maskingtape away from the surface. The poor edge definition obtained by the useof masking tape often requires the use of a decorative stripe to hidethe fuzzy paint edge.

[0027] Another application involves a high heat tape capable ofwithstanding the paint baking temperatures that auto bumpers aresubjected to as a post cure phase in the paint process. Poor edgedefinition is a constant quality control problem in the auto paintingprocess.

[0028] The present invention is also capable of application in themoulding industry, particularly in the trimming of moulded materials.When parts are moulded in a closed injection mould, there is typicallyan allowance in the mould for material to flow beyond the mould toensure that the cavity is completely filled. The excess material,generally called the flash material, is commonly removed by variouscutting methods subsequent to the moulding operation itself. It iscontemplated by the present invention that a groove be formed into thebody of the mould at the precise edge of the moulded part correspondingto the edge to be trimmed to remove the flash material. A bare wire,which may be square in profile to assist in its retention and to preventthe entry of material into the groove during the moulding operation, maythen be placed in this groove in such a way that removal of the wireafter the moulding process produces a clean cutting action in theprecise location for trimming the flash and at the same time results ina clean groove for the next cycle of use.

[0029] The filament may alternatively be applied to, or positionedadjacent, such a groove machined into the mould body by embedding thefilament inside an extruded material such as rubber or silicone. In thisway, the filament itself could be of a diameter or dimension muchsmaller than that of the groove and be positioned to be pulled along theinside edge of the groove to produce a cutting line at the appropriateedge of the moulded part.

[0030] The aforementioned extrusion could itself be manufactured with aprofile that complimented the form of the groove so that the extrusionis held securely in the groove once it has been applied, by means of aninterference fit. The filament so incorporated in the extrusion may beseparated from the extrusion when pulled, and escapes the groove tocomplete the cutting process. The extrusion remains in place in thegroove until it is removed as the last step before the mould is readiedfor another cycle.

[0031] Grooved moulds may be used, for example, in the fiberglassmoulding industry which typically uses open mould processes. The timingof the trimming of a fiberglass part is critical as the part must be cutbefore the resin cures to a hardness that does not permit the applicatorto cut it with a knife.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is an end view of a piece of adhesive tape of the presentinvention, showing the stages of preparation of the tape.

[0033]FIG. 2 shows a method of using the adhesive tape of the presentinvention.

[0034]FIG. 3 is a schematic view of an apparatus that may be used toprepare the adhesive tape of the present invention.

MODES FOR CARRYING OUT THE INVENTION

[0035] The method of the present invention may be more readilyunderstood by referring to the attached drawings.

[0036] Referring first to FIG. 1, there is shown a self-adhesive tapethat is particularly suited to the application of the present invention.The tape 30, as shown in FIG. 1-6 essentially comprises a foldedadhesive layer 28, at one edge of which is a filament 24, retained inplace by the adhesive layer 28. The adhesive layer may be a non-adhesivesubstrate coated with a conventional adhesive material, or may, in somecircumstances, comprise a film of adhesive material.

[0037] As discussed in more detail below, the filament may be retainedin place at the edge of the adhesive tape by folding the tape over thefilament to envelope the filament within the adhesive tape, as shown inFIGS. 1-1, 1-2, 1-3 and 1-4. As further shown in FIG. 1, a layer orsubstrate of non-adhesive, easy-to-release material 26 and 27 may beapplied to each of the adhesive surfaces of the self-adhesive tape, topermit the tape to be handled and stored without adhering to othermaterials. The construction of such an adhesive tape is referred to inmore detail below.

[0038] As can be seen by reference to FIG. 1, the adhesive of thepresent invention may be prepared from conventional, double coatedadhesive tapes such as those sold by the 3M Company, which generallycomprise an adhesive layer consisting of a substrate coated with anadhesive, and a non-adhesive release layer which is applied to theadhesive layer to protect the adhesive material. The non-adhesive layeris coated on both sides with a release material so that, when thematerial is rolled as is commonly done, the non-adhesive layer isbetween each adhesive layer.

[0039] To prepare the adhesive tape of the present invention, therelease layer applied to a conventional, two-sided adhesive tape may becut lengthwise, such that the release layer, but not the adhesive layer,is cut and is then bent or folded to bring the exposed adhesive surfacestogether. Concurrently, the filament is applied to the adhesive surfaceat the fold so that, once folded, the filament is located at one edge ofthe folded tape. One portion of the release layer may be removed, andfilament-containing adhesive tape re-rolled to provide the adhesivetrimming material of the present invention.

[0040] Referring now to FIG. 2, there is shown a surface 53 to which isapplied the self-adhesive, filament-containing tape which isparticularly suited to the method of the present invention. As shown inFIG. 2, the surface comprises an area A which is intended to be coveredwith a protective coating, and Areas B and C which are not intended tobe covered with a protective coating.

[0041] The tape 30, containing a filament 24, is applied to the surfaceso that the filament 24 lies along the edge of the area which is to beprotected. Additional masking material 55 may be applied to the tape toprotect the area which is not to be coated, and adhered to the adhesivelayer 28.

[0042] The ends of the filament 24 may be left exposed, and extend awayfrom the surface, so that they are accessible after the application ofthe coating material. As shown in FIG. 2-4, coating material is appliedto the surface, covering the area A and the masking tape 30, and themasking material 55. As soon as the material has cured sufficiently tobond to the surface and maintain a defined edge, the filament 24 isdrawn upwardly through the material, cutting the material at the desiredlocation. The masking materials 55 and the tape 30 are then removed,leaving the coating in the desired location.

[0043] Shown in FIG. 3 is an apparatus particularly adapted tomanufacture the trimming material of the present invention. According tothe present invention, there is provided in FIG. 3 a bulk wire spool 21rotatively mounted on a spindle, and which may be controlled by amagnetic brake tensioning device 35 which is adapted to maintainrelatively constant tension in the wire 24. The wire 24 isconventionally manufactured in a manner that it is wound from side toside on the spool 21, and there are consequently provided a guide wheel10 and wire positioning wheels 11 that are intended to centre the wireas it is unwound from the spool 21. Also provided is a bulk roll 41 ofadhesive tape, with a center slit release liner, which may also becontrolled by a magnetic brake tensioning device 35. Both the wire 24and the tape 23 are pulled through the apparatus of the presentinvention by the drive apparatus 40 described in more detail below.

[0044] As the wire 24 is unwound from the bulk roll 21, it is centred byguide wheel 10 and positioning wheels 11 so that it is positioneddirectly above the center of the adhesive tape 23. As the tape 23 passesover wheels 14, 15 and 16, it is folded by the increasingly steepV-groove of wheels 15 and 16 about the center slit, and the filament 24is brought into contact with the adhesive tape 23 and forced into anadhesive contact with tape 23 immediately above the center of the liner.

[0045] It should be noted that while the rotating wheels 13, 14, 15 and16 are shown in FIG. 3, stationary guide posts or other appropriatemeans for progressively folding the tape could be used.

[0046] The tape 23 now in contact with the filament 24 passes through adrive assembly generally designated as 40 and comprising drive wheels 42and 43, which force the adhesive sides of the tape 23 together, and pullboth the tape 23 and filament 24 through the apparatus. One portion ofthe release liner 26 may be removed at this point by the use of anadditional drive wheel 44, which pulls the liner 26 around a guide post48 and leaves one adhesive side of the adhesive tape 30 exposed. Thefilament containing adhesive tape 30 is then rolled on to spools 51. Thedrive mechanism comprises a motor 31, suitably connected by belts andpulleys to the drive mechanism 40 and the winding mechanism 50, to pullthe material through the apparatus and cause it to be rewound on spoolscontaining an appropriate amount of the material.

[0047] It will be understood, of course, that modifications to theapparatus disclosed above would be relatively apparent to one skilled inthe art, and could be made without departing from the spirit orsubstance of the invention herein described. In particular, the presentinvention contemplates embodiments in Which the substrate to which thefilament is to be applied is itself the adhesive layer, so that onelayer of the lining or masking layer is avoided. In addition, thefilament may be applied to the adhesive substrate in situ, that is,after the adhesive substrate is applied to the surface to be coated, orcontemporaneously with the application of the substrate to that surface.

1. An filament-bearing adhesive tape comprising an adhesive substrateadapted to be releasably adhered to a surface to be coated, and afilament releasably adhered to an edge of that substrate.
 2. A method oftrimming a coating applied to a surface comprising (a) applying to thesurface to be coated a masking material to define the area to be coatedand a filament of material of sufficient tensile strength to cut thecoating material; (b) applying coating material to the surface; (c)allowing the coating material to dry or cure until it obtains sufficientstrength to hold a cut edge; and (d) drawing the filament through thecoating to cut the coating.
 3. An apparatus for making a filamentbearing adhesive tape comprising (a) means for folding an adhesivesubstrate along a predefined line; (b) means for applying a filament tothe interior of the fold so formed; (c) means for closing said fold toretain said filament at the edge of the filament bearing tape.